1. Field of the Invention
The invention is directed to a patient comfort system that includes pneumatic convective devices receivable on a human or animal body which receive a stream of pressurized, thermally conditioned air, distribute the pressurized air within a pneumatic structure, and emit the air through one or more surfaces for convective transfer of heat between the thermally conditioned air and the body. In particular, the invention is directed to the warming of human or animal bodies in a clinical setting by measures that adapt pneumatic convective devices for use with clinical garments, thereby providing thermal treatment to wearers of such garments while permitting movement of the user and enhancing clinical convenience.
2. Description of the Related Art
Pneumatic devices which transfer heat between thermally-conditioned air and a body are known. For example, there are inflatable pneumatic devices that receive a stream of pressurized, warmed air, inflate in response to the pressurized air, distribute the warmed air within a pneumatic structure, and emit the warmed air onto a body to accomplish such objectives as increasing comfort, reducing shivering, and treating or preventing hypothermia. These inflatable devices are typically characterized as “blankets” or “covers”. Arizant Healthcare Inc., the assignee of this application, makes and sells such devices under the BAIR HUGGER® brand. One such device is the Model 522 Upper Body Blanket.
Inflatable pneumatic warming blanket or cover devices are adapted especially for use with supine persons and are typically deployed by being laid directly on a person lying on a bed, a gurney, or a surgery platform, so as to drape over or cover some portion of the person. Because these devices are designed to cover and hang about or over a supine person, they are not easily or readily deployed on persons who are standing, sitting, reclining or moving. In particular, inflatable blankets are not suitable in a clinical setting in which it is desirable to warm a patient, and also necessary that the patient be able to move about and between various postures. In addition, there are a variety of clinical settings in which patient warming is desirable, with each setting requiring its own unique access to patient anatomy that may not be afforded by an inflatable blanket. For example, examination or treatment of a patient in a primary acute care unit (PACU) could call for access to patient lines in the chest area, setting IV's in the arm, application of a stethoscope to the back and/or side, or application of a blood pressure cuff. Further, patient mobility throughout a clinic or a hospital is highly desirable, but would be severely curtailed with use of inflatable blankets. For example, transporting a patient to an x-ray or MRI location in a wheelchair, would be made problematic with an inflatable blanket.
There is also an advantage in not changing established and familiar algorithms of care in which both patients and nurses deal with clinical garments, such as gowns, and nurses know how to deliver care in all circumstances where a patient is wearing a clinical garment. If an inflatable blanket were to be used for warming, a new algorithm would be required to deal with this new element in clinical practice.
One attempt to adapt an inflatable pneumatic blanket for non-supine postures is embodied in U.S. Pat. No. 5,697,963, assigned to Augustine Medical, Inc. and incorporated by reference. In this adaptation, an inflatable pneumatic blanket having a head-section drape is provided with an aperture in the head section drape that is large enough to accommodate the head of a person sitting in a chair. However, this adaptation has a limited use in that a person using it must remain in a sitting or reclining posture in order for the device to drape over the person's body and retain warmed air and heat about the person. Such devices are not designed to accommodate movement or changes in the person's posture or to allow easy access to patient anatomy. These devices are meant to treat hypothermia by driving calories into the patient.
Other inflatable pneumatic warming devices designed for use with supine persons employ tubular structures to at least partially surround a person, and utilize sheets of material extending across the person and the structures to retain warmed air and heat about the person. These devices are even less adaptable than blanket devices for non-supine uses. See, for example, U.S. Pat. Nos. 5,300,101 and 5,674,269, which are incorporated by reference.
A need exists for a pneumatic convective device that achieves the objectives of increased comfort, reduced shivering, and treatment or prevention of hypothermia in a clinical or medical office setting where patients must be able to change postures and enjoy a certain amount of mobility without a significant impact on or change to the treatment algorithm. For example, when visiting a physician for an examination, a patient may be ushered into an examination room, asked to remove clothing in order to permit examination, and given a thin cloth gown to wear while awaiting the physician. In this environment, the patient may be chilled, may shiver, or may be in a condition conducive to hypothermia. Patient anxiety is frequently exacerbated by this cold discomfort. Concomitant with a heightened level of anxiety, patients perceive time as slowing and this anxious waiting period can seem to be prolonged. The cold discomfort can cause a one hour wait to seem like 2 hours to the patient. People tend to vasoconstrict when frightened, and vasoconstriction can lead to reduced peripheral temperature and increased blood pressure, and can make IV access much more difficult. Finally, there is evidence that feeling cold increases the perception of pain. A thin cloth gown provides little in the way of insulation, warmth, and comfort in such circumstances. Therefore, in addition to the patient satisfaction and comfort produced by a bath of thermally-treated air, providing warmth to a cold patient in a medical setting should produce the following unexpected benefits: 1.) reduced blood pressure and easier IV access; 2.) reduced pain sensation; 3.) normalizing of the patient's perception of time slowing; 4.) reduced anxiety and reduced need for medication. These and other objectives are realized when a patient is maintained in a state of thermal comfort. In this regard, “thermal comfort” for a person is defined by P. O. Fanger as “that condition of mind which expresses satisfaction with the thermal environment”. Fanger, Thermal Comfort: Analysis and Applications in Environmental Engineering, Danish Technical Press, Copenhagen, 1970.
It would be advantageous to provide a course of action, a method, or an instrument by which a patient could be maintained in a state of thermal comfort characterized by a comfortable, healthy temperature while awaiting the physician and even while undergoing examination or treatment. An inflatable blanket or cover could be deployed for this purpose, but would be very impractical because the patient would be required to remain supine or maintain a prone or sitting position. Clinical convenience and utility dictate a more flexible solution in which a pneumatic, convective device serves a warming function in one or more forms that permit movement of the user and of the device itself on the user for examination. It would be particularly advantageous if the solution comported with present modes of treatment that presume the use of clinical garments. For optimal heating, such forms should focus or concentrate the convective effect on the portion of a body being warmed that has the highest concentration of cutaneous thermal receptors. This portion includes the head, neck, chest and abdomen.
Pneumatic devices that thermally condition persons while standing and/or moving are known. One such device, described in U.S. Pat. No. 4,457,295 incorporates a pneumatic, convective means into an article of clothing that is intended for heavy-duty use in an unfriendly environment. The objective of this device is to warm and ventilate by general application of pressurized, heated air through the inside of a closed article of clothing. The pressurized, heated air is provided through a valve system from a source that is convenient to a particular unfriendly environment, such as an exhaust manifold of a motorcycle engine. The article of clothing is fitted to the wearer's body and is closed in order to afford protection against the environment in which the device is deployed. Thus, the device further requires a means for ventilating moisture from within the article of clothing. Its normally closed configuration and complicated pneumatics make this device inconvenient and impractical to use for patient comfort in a clinical environment.
A pneumatic garment, described in U.S. Pat. No. 3,468,299, includes a hooded overcoat intended to be used in unfriendly environments for heating and ventilating a person. This device's structure and operation make it also unsuitable for use in maintaining patient comfort in a clinical environment.